Inspection Procedure J-2
INSPECTION PROCEDURE J-2: Headlight, Taillight: Headlights (low-beam) do not illuminate.
Connector:
CIRCUIT OPERATION
- If the headlight switch signal from the column switch turns on, the front-ECU makes the headlights illuminate. Whenever the headlights illuminate, the low-beam lights illuminate due to the headlight dimmer switch automatic resetting function.
- If the SWS communication line is defective, the low-beam headlights will illuminate by using other signal line (headlight back-up circuit).
TECHNICAL DESCRIPTION (COMMENT)
The column switch or the front-ECU may be defective.
NOTE: If only one of the headlights does not illuminate, the light bulb may be burned out or the wiring harness between the light and the front-ECU may be defective. In this case, check the circuit by referring to Headlight. Headlamp
TROUBLESHOOTING HINTS
- The column switch (turn-signal light and lighting switch) may be defective
- The front-ECU may be defective
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
DIAGNOSIS
Required Special Tools:
- MB991223: Test Harness Set
- MB991502: Scan Tool (MUT-II)
- MB991529: Diagnostic Trouble Code Check Harness
STEP 1. Check the DTC.
Q: Doe the DTC set when the ignition switch is turned to the "LOCK" (OFF) position?
YES : Carry out the troubleshooting by referring to Diagnostic Trouble Code Chart. Trouble Code Diagnostic Charts
NO : Go to Step 2
STEP 2. Check the input signal (by using scan tool MB991502).
Check the input signal from the headlight switch.
CAUTION : To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Check that the tone alarm of scan tool MB991502 sounds when the input signal enters.
Q: Does the tone alarm of scan tool MB991502 sound when the input signal enters?
YES : Go to Step 4.
NO : Check the headlight switch input circuit. Inspection Procedure O-14
STEP 3. Check the input signal (by using a voltmeter).
Check the input signal from the headlight switch.
1. Use special tool MB991529 to connect a voltmeter between ground terminal 4 or 5 and ETACS-ECU terminal 9 of the data link connector.
2. Check that the voltmeter indicator deflects once when the input signal enters.
Q: Does the voltmeter indicator deflect?
YES : Go to Step 4.
NO : The voltmeter needle does not fluctuate when the lighting switch is turned from "TAIL" to "HEAD": Refer to Inspection Procedure O-14 "The headlight switch signal is not sent to the ETACS-ECU." Inspection Procedure O-14
YES : Go to Step 4.
STEP 4. Check the battery power supply circuit to the front-ECU. Test at front-ECU connector A-10X.
1. Disconnect front-ECU connector A-1OX and measure the voltage available at the relay box side of the connector.
2. Measure the resistance value between terminal 3 and ground, and also between terminal 4 and ground.
- The voltage should equal approximately 12 volts (battery positive voltage).
Q: Is the measured voltage approximately 12 volts (battery positive voltage)?
YES : Replace the front-ECU. Check that the tail lights illuminate normally.
NO : Go to Go to Step 5.
STEP 5. Check front-ECU connector A-10X for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is front-ECU connector A-1OX in good condition?
YES : Go to Step 6.
NO : Repair or replace the damaged component(s). Refer to Harness Connector Inspection. The headlights (low-beam) should illuminate normally.
STEP 6. Check the wiring harness between front-ECU connector A-10X (terminal 3 and 4) and battery.
Q: Is the wiring harness between front-ECU connector A-10X (terminal 3 and 4) and battery in good condition?
YES : Replace the front-ECU. The headlights (low-beam) should illuminate normally.
NO : The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. The headlights (low-beam) should illuminate normally.
Check the wiring harness between front-ECU connector A-10X and headlight connector (LH) A-24and headlight connector (RH) A-35.
NOTE: After checking The intermediate connector C-5, check the wires. If intermediate connector C-O5 is damaged, repair or replace it. Diagnostic Aids
Q: Is the wiring harness between front-ECU connector A-10X (terminal 3 and 4) and battery in good condition?
YES : Replace the front-ECU. The headlights (low-beam) should illuminate normally.